1. Field of the Invention
The present invention relates to a method of connecting an optical fiber to a planar optical waveguide, and more particularly, to a connection method which permits easy, low-loss connection of an optical fiber to one of planar optical waveguides formed in an optical component.
2. Description of Related Art
When constructing an optical communication system, optical waveguide chips are used as optical components. Optical waveguide chips are generally classified into those in which silica glass is deposited on, e.g., a Si substrate whose refractive index is different from that of the silica glass, to form planar optical waveguides, and those in which semiconductor thin films of various compositions are successively formed on a special semiconductor substrate of, e.g., InGaAsP, to form planar optical waveguides.
In order for an optical waveguide chip to properly function as an optical component in an optical communication system, optical fibers are connected to the planar optical waveguides formed in the optical waveguide chip, with each axis thereof aligned with each axis of the planar optical waveguides, so that light can be transmitted from one optical fiber to the other through the planar optical waveguide.
In general, optical fibers are connected to planar optical waveguides in the following manner: First, the optical waveguide chip is positioned and fixed in a specific casing, and an optical fiber is abutted against one end of the planar optical waveguide. With light entered from the other end of the planar optical waveguide, the optical fiber is shifted relative to the planar optical waveguide, and while the optical fiber is located at a position where the intensity of light transmitted therethrough is a maximum, the fiber is firmly bonded to the planar optical waveguide by an adhesive or the like.
Subsequently, another optical fiber is connected to the other end of the planar optical waveguide in a similar manner. Namely, with light transmitted through the previously connected optical fiber, the optical fiber to be connected is positioned and bonded to the planar optical waveguide.
In the connection method described above, there is employed no particular mechanical member which keeps each axis of optical fiber aligned with each axis of the planar optical waveguides formed in an optical waveguide chip, for preventing unwanted movement after axis alignment procedures. Thus, the connection reliability is low, possibly causing an increase of the connection loss, when the connection is subject to temperature variation or external stress.
Further, the above connection method requires considerable time for the abutting of the optical fiber onto the planar optical waveguide, preparations for the transmission of light to the optical fibers, preparations for the measurement of the intensity of output light, etc. In addition, expensive apparatuses are needed for the positioning of the optical fibers and the optical waveguide chip.